After an amputation, the stump which remains is commonly protected by a stocking or liner to shield the skin from direct contact with the prosthesis. Within one to two weeks after the amputation, a post-operative prosthesis can be worn temporarily, perhaps for a period of about two weeks to about two months. During this time the stump heals, swelling reduces, and the stump ultimately takes its final shape. It is common practice during this early post-operative period to apply a thin stocking of knitted fabric to the stump, along with one or more outer layers of padding wrapped around the stump. Common wrapping materials used for this purpose are a resilient foam or felt, or a similar material known by the trademark Webril. Over this outer layer is wrapped a rigid dressing of plaster or other similar synthetic materials to form a rigid socket for a temporary prosthesis. A pylon and prosthetic foot are attached to the socket for form the temporary prosthesis, which enables the patent to become ambulatory shortly after the amputation.
The technique of wrapping different types of available padding around the stump and then forming a temporary prosthetic limb around this wrapping is cumbersome and time-consuming. The resulting temporary prosthesis with the extraneously added padding are not always comfortable for the patient, nor is it convenient for the patient to remove and re-apply such a temporary prosthesis. In addition, there is a need to ensure that such a temporary prosthesis does not produce discomfort to the patient when the patient is ambulatory on the temporary prosthesis.
Once healing is completed, the permanent or "definitive" prosthesis is assembled by the prosthetist. The permanent prosthesis includes a stump socket made from a cast that matches the shape of the stump. A pylon attached to the stump socket carries a prosthetic foot. A liner is worn by the patient to protect the skin from direct contact with the inside of the socket. The liner is commonly form-fitted to a cast of the stump socket to match the shape of the patient's stump. One prior art liner for stump sockets is made from a material known by the trademark Pelite, a closed cell plastic foam material which has to be heat-formed on a cast to shape it to match the inside of the stump socket. Pelite is a relatively firm closed cell foam material which provides some cushioning. It also resists compression as well as twisting of the stump relative to the socket; and discomfort often can result. Another prior art liner for stump sockets is custom-made from a material known by the trademark Kemblo, a composite leather and foam rubber liner. The leather is molded onto a cast to match the inside shape of the stump socket. The rubber is then glued onto the leather liner in strips. It requires several hours for the prosthetist to make a liner by this process.
The process of custom molding a liner for the definitive prosthesis is time-consuming and expensive. Moreover, this cost is amplified because these liners wear out and require replacement by further custom-made liners. Further, if the patient gains or loses weight the volume of the stump changes; so there is an ongoing need to provide a liner that accurately and comfortably fits between the stump and socket of the permanent prosthesis.